Manufacture of electric filaments.



UNITED STATES PATENT OFFICE.

vCARL AUER VON WELSBACH, OF VIENNA, AUSTRIA-HUNGARY, ASSIGNOR TO WELS-IBACH LIGHT COMPANY, OF GLOUCESTER CITY, NEW JERSEY, A CORPORATION OFNEW JERSEY.

MANUFACTURE OF ELECTRIC FILAMENTS.

No Drawing.

To all whom it may concern:

Be it known that I, CARL AUER VON Wnns- BACH, a subject of the Emperorof Austria- Hungary, residing at Vienna, Austria-Hungary, have inventedor discovered a certain new and useful Improvement in the Manuand whichwill give forth a very brilliant "light.

I accomplish this result by constructing the illuminant substantially ofthe metal osmium, a substance which 18 readily O X1- dizable if heatedin an atmosphere conta1ning oxygen, but which, especially when pure, canwithstand without melting or volatilizing a temperature above thevolatillzmg temperature of platinum if placed an 'vacuo or in certainprotective gases (as, for inst ance, the gases and vapors incident tothe incomplete combustionof illuminating gas, procured by the ignitionthereof at the a r feed openings of a Bunsen burner, as herelnaftermentioned.) It is therefore capable'of being raised to so high atemperature that the light emission bears a higlrraho to the consumptionof energy and this great efficiency is obtained without destroying thedurability of the filament. There are however great difficulties in theuse of this metal and up to the present time no means have been found bywhich it can practically be applied to the above purpose. It is notductile! but on the contrary exceedingly brittle and pulverizable and itcannot be formed into wires either by drawing orepressure. Therefore toutilize it in the manufacture of filaments suited for use inincandescence electric lamps involved the devising of special methodsfor that purpose.

Osmium was known to be a good eonductor of electricity, yet it was notknown that it is non-volatilizable, when in vacuo or in certain reducinggases, at temperatures at which platinum volatilizes; a discovery whichis utilized as one of the bases of the present invention. Now I havediscovered that osmium while under the influence of the electric currentat very high temperatures,

Specification of Letters Patent.

Patented Nov. 22, 1910.

Application filed August 9, 1898. Serial No. 688,201.

either in ormuo or in certain reducing protective gases, assumes apartially fused c0- herent or cinder like condition which causes anintimate contact of the particles whereby is obtained perfect electricconductivity and requisite flexibility and elasticity, while at the sametime resisting a liquefying action even at such high temperatures. T hismaintaining of its solid form, when the heating is effected in thepresence of certain gases or in vacuo such as that of the ordinaryelectric lamp, and the refusal to liquefy or volatilize continuing up totemperatures much higher than that at which the volatilization ofplatinum occurs, is a discovery utilized in my present invention, and animportant fact to keep in mind when it is remembered that the metalosmium (among those of its group of highly infusible metals) 1s peculiarin that it oxidizes with great readiness when in the presence of freeoxygen.

In carrying out my invention I prepare a stiff uniform paste or osmiumor its suitable salts, and a binding material which under the influenceof heat will resolve itself practically into carbon. I take osmium in avery finely divided condition and a binding material, such as a syrup ofsugar, which I thoroughly knead into a smooth stiff paste throughoutwhich the particles are intimately and uniformly distributed. Of thebinding material I use only sufiicient to hold the particles togetherduring the manufacture of the filament.

If a dry binding material be used a suflicient quantity of water must beused to enable the ingredients to assume the desired pasty condition.Viscous collodion may be used as the binding material in which case thepaste after it has been given the filamentary form and before furthertreatment must be denitrated. This paste, which I shall hereafterdesignate as my osmium paste-is then given its filamentary form by beingforced through a suitably shaped die or in any other suitable manner; Ihowever prefer to form it into what I shall hereafter term my osmiumthreads by forcing it' through a suitable die for that purpose.

My osmium threads after drying are then subjected to dry or destructivedistillation. The application of heat resolves the organic matter intocarbon and volatile constituents which are driven ofl", so that thefilament now comprises a mixture of carbon and osmium. The carbon isthen removed from the mixture by subjectin the incomplete filament tothe influence o a moderate heat obtaiiied by an electric current in anatmosphere of gases capable of' taking u moving the carbon Withoutoxidizing the osmium, and the osmium particles are partially fused orcemented together by continulng the current to the development of a heatat which platinum would volatilize. Such an atmosphere should containcarbonic acid or vapor'waterto take up the carbon, but, as these gaseswould attack the osmium more or less, the atmosphere should also containa reducing gas, such, for instance, as hydrogen, carbon monoxid, orhydro-carbons. The simplest composition of such an atmosphere would behydrogen containing water vap r, or carbonic acid, or a'mixture ofcarbon-monoxid and carbonic acid. A very suitable mixture for thatatmosphere may be derived, for instance, from the mixture of gases andvapors incident to the incomplete combustion of illuminating gasprocured by the ignition thereof at the base of air feed openings of aBunsen burner, the said mixture of gases and vapors being collected fromthe burner tube.

In practice I mount the incomplete filament in a suitable containerfilled with the described gas and then apply the electric current forthe elimination of the-carbon at a moderate heat and the consolidationand cementation of the .particles into a dense, compact and coherentfilament of osmium at a heat at which platinum would volatilize. Thus bythe action of the electric current and the heat developed thereby, whilethe filament is in the presence of an atmosphere of the protective gas,the carbon is eliminated and the osmium particles cemented into acomplete dense coherent filament which incandesces at a temperatureabove that at which platinum volatilizes and is consequently of greatefliciency as an incandescent electric filament. The filaments thusproduced are readily distinguishable in that they are free from carbon,extremely dense and coherent, have the necessary flexlbility andresiliency or elasticity, and depend upon osmium not only for theirconductivity, but for the incandescence which is produced at atemperature at which platinum would be melted.

The osmium short of absolute purity contains certain oxids as impuritieswhich are not entirely volatile even when brought to dazzlingincandescence in an atmosphere of prrotective gas, yet they may bevolatilized oxids, such as titanic acid, alumina, magnesia, and the likewhich are more volatile, and volatilize when brought to incandescence.With osmium in a state of absolute purity the metallic particles aremore readil and thoroughly consolidated and cemente into a stable,dense, homogeneous, coherent and elastic filament, so it is of thegreatest importance to eliminate all such oxids from the osmium of myosmium threads to permit of a more intimate contact of the metallicparticles and that I do by adding to my osmium paste a suitable quantityof titanic acid or. an oxid which volatilizes when brought toincandescence and then treating the threads made therefrom in the samemanner as my hereinbefore described osmium threads in which treatmentthe titanic acid, or other oxid used for the purpose will be volatilizedand the impurities eliminated by their volatilization when the filamenthas reached a dazzling incandescence in the rotective gas following theelimination of the carbon from the binding material which takes place ata lower temperature.

In carrying out this process of refining the osmium and theconsolidation of its particles I prefer to use titanic acid though theremay be used to advantage all oxids of a more basic character which willvolatilize when brought to incandescence as for example alumina andmagnesia. Silicic acid will not answer the purpose. However thoria andzirconia may be used for the removal of the impurities in which casethese oxids would appear as a coating firmly the titanic acid, or oxidused, in a very finely divided condition and add it to the very finelydivided osmium and binding material that it may be thoroughl andintimately incorporated therewit into a smooth, stilf, uniform pasteconsisting of osmium, titanic acid, or whatever oxid may be used, and asuitable bindin using of osmium and titanic aci or of the oxid used,their corresponding chemical equivalent in wei hts, as for example tenparts in weight 0 osmium and four parts in weight of titanic acid. Thepaste is then given its filamentary thread-like form as' hereinbeforefully set forth.

The surface of the threads or whatever the form may be, should be smoothand nearly brilliant, otherwise they should be rolled betweenmirror-glasses which are parallel to,

and of a certain distance from each other and coated with smooth paperor similar material. Then the filamentary threads are while still in aflexible condition formed into the required shape, although they may ata subsequent stage in the treatment be given om the osmium in thepresence of other their final desired form and treated throughmaterial,I

tric current, in a suita out in the manner hereinbefore' set forth.

In carrying out that treatment after the osmium thread has been laced inthe eleclile protective gas such as heretofore described, I apply thecurrent, first slowly and until the carbon of the binding material hasbeen eliminated, but afterward intensely heated to a condition ofdazzling incandescence when the titanic acid is volatilized and theimpurities eliminated,-this should not'be eflected too quickly,-leavingthe osmium in a state of purity as a stable, dense, ho ogeneous,.coherent and elastic filament 0 great .durability suitable for use asthe filament in an electric lam when placed in vacuo or suitableprotective gas and heated to incandescence at a temperature above thatat which platinum volatilizes when it will emit an intensely brilliantlight. A peculiarity of my osmium filament is that it will for a long'time withstand a temperature above that at which platinum volatilizes.The completed filament is now ready'for mounting in the lamp bulb,-beingconnected to the leadingin wires by an osmium cement as set forth in myapplication of even date herewith,-

which is filled with the protective gas, and

as a firmly united enamel-like coating on the surface of the osmium.Taking thoria as the example I would, if it is to be added to the paste,make use of, for example, three parts osmium, one part. thoria. andthree tenths parts alumina with. the necessary suitable bindingmaterial, thereafter treating the paste and the threads made therefromthe same as hereinbefore set forth, and I find that when brought to highincandescence in the protective gas the alumina is in whole or partvolatilized. the impurities eliminated. while the thoria appears as afirmly united enamel-like coating on the surface of a dense. coherentcore or wire of osmium, thus producing a'strong and durableosmium-thoria-coated filament, that will incandesce at temperaturesabove that at which platinum volatilizes and emitting an intenselybrilliant light.

(While I prefer to use alumina it may however be omitted as aningredient in the last mentioned paste the thoria alone acting as thepurifying agent. Ifzirconia be substiis the case of the paste, beomitted.

tuted either in whole or part for the thoria it should as an example beused in correspondingly chemical equivalent in weight. If applied as acoating to the already formed osmium filament I make a smooth uniformpaste of a cream-like consistency of, for example, three parts thoriaand one part alumina which I apply to the filament with a brush or inany other suitable or convenient way so long as the filament isuniformly coated with the paste, and so coated I again subjectthe'filament to high incandescence in a protective gas which under theinfluence of the heat and the electric current leaves the oxid firmlyunited 0r cemented as an enamel-like coating on the surface of theosmium filament producing as in 'the former case a dense coherentosmium-thoria-coated filament possessing the properties andcharacteristics heretofore mentioned. Zirconia may be substituted forthe thoria using it for example in corresponding chemical equivalentweight. The alumina may. as The osmium thread may before it is subjectedto electrical treatment, be coated in like manner and then electricallytreated as herein specified for the production of an osmium filament.

Having thus described my invention what I-claim as new and desire tosecure by Letters Patent is 1. An incandescent filament for an electriclamp consisting of osmium in a dense, coherent and elastic conditionincandescing at a temperature at which platinum volaa self sustainingthread or wire like filament substantially as setforth.

3. A filament for an electric incandescent lamp composed of a series ofosmium particles electrically welded into a dense coherent and elasticself sustaining strip or thread which will incandesce at a temperatureabove that at which platinum melts substantially as set forth.

4:. A dense, coherent and elastic strip or thread of osmium'which whenused as the filament in an electric incandescent lamp will incandesce ata temperature above the melting point of platinum substantially as setforth.

A filament for an electric incandescent lamp composed of osmium and acoating of thoria. substantially as set forth.

' 6. The process of producing filaments for incandescent electric lamps.which consists in forming-a threadlike body from a paste containing arefractory metal and an agglutinatin 'material, eliminatin from saidthreadlike body the agglutinatlng constitueut thereof in a protectingenvironment, thereby leaving a corresponding thread-like body. ofmetall1 c part-1 c es, an progressively consolidatmg and uniting sa1 dparticles into a compact, coherent, elastic final filament, by thepassage therethrough of an electric current at a heat finally reachingdazzling incandescence; substantlally as described.

7. The process of producing filaments for incandescent electric lamps,which consists in forming a thread-like body containing a refractorymetal, subjecting it to the action of an electric current until 1t isconverted into a series of metallic particles preliminarily sinteredtogether, and then progressively raisin the temperature of' said body bya gradua increase of the current until the preliminarily sinteredparticles are united into a compact, coherent, elastic filament;substantially as described.

8.The herein described process of making filaments for incandescentelectric lamps from a thread composed of acarbonaceous material, andosmium, consisting in distilling ofii' the volatile constituents of thecarbonaceous matter, and then removing the carbon by subjecting thematerial to theaction of an electric current'in the presence of-a gaswhich will combine with the carbon but which is inert with respect tothe metal, and by the action of electric current causing the particlesto cohere substantlally as set forth.

9. The process of making filaments for incandescent electric lamps,which consists in forming a pastecontaming carbonaceous matter andosmium, forming said paste into the desired filamentary shape,distilling off the volatile constituents of the carbonaceous matter, andthen removing the carbon by subjecting the material to the action of anelectric current in the presence of a gas which will combine with thecarbon but which is inert with respect to the metal and by thecontinuous action of the current causing the particles to cohere intoathread or wire like filament substantially as set'forth.

10. The process of making filaments .for incandescent electric lamps,from a paste of collodion, and osmium, which consists in forming theincandescent body therefrom,

denitrating the collodion and subjecting the same to the action of theelectric current in the presence of a gas which unites with the carbonand which will be inert to the metal,

and by continuing the current cementing the metallic particles into aself sustaining filament, substantially as set forth.

-- 11. The herein described process of making filaments for incandescentelectric lamps from a paste of osmium, thorium, alumina and a bindingmaterial, consisting in molding the paste into a suitable wire or threadlike form, subjecting the sameto dry distillation and afterwardeliminating the binding material by the heat of an electric currentpassing through the filament in the presence of a suitable atmosphere ofgases, and by the continuous action of the electric current causing theparticles to cohere into a dense, coherent and elastic incandescentfilament substantially as set forth.

12. The herein described rocess of making a filament for incan escentelectric lamps from a paste of osium, titanic acid and a bindingmaterial, consisting in molding the paste into a suitable wire or threadlike form, subjecting the same to dry distillationin a protective gasand eliminating I the binding material by the heat of an electriccurrent passing through the filament in the presence ofa suitableatmosphere, and by the continuous action of the electric current and ata temperature above the melting point of platinum 'volatilizing thetitanic acid and eliminating the impurities and causing the particles tocohere into a dense,

coherent and elastic incandescent substantially as set forth.

13.- The process of making a filament for filament incandeseentelectriclamps' from a paste of 'osmium-, an,.ox'1d of more baslc character whichvolatillzes when brought to meandescence and a binding material,consisting in molding the paste into a'suitable wire 'or thread likeform, subjecting the same to dry distillation in a protective gas andeliminating the binding material by the heat of an electric currentpassin through the filament in the presence of a sultable atmosphere,and by an increase of the electric current developin a heat at which theoxid volatilizes an eliminates the impurities and causes the particlesto cohere into a dense, coherent oxid used, is volatilized and the imurities eliminated and the osmium cemente into a state of purity as astable, dense, homogeneous, coherent and elastic filament substantiallyas set forth.

15. The PIO0%S of making filaments for .incandesceht v,e'lect ric lamps,whih cbnsists pact, colierent elatic filamentg' substantiaily inproducing 'athread-like body of loosely- 'as described. v coherentmetallic pal-tides, and 'then. pro- 'Signed this 27th day of J ulv 1898.

' gressively raising the temperature of said- CARL AUER VON VELSBACH;body to dazzling incandescence,by the pa 'Witness'es: I 4

sagetherethrough of an electric current Ltjmwm HAITINGE,

. 'u til said pa'l ticles a1"e united into a. com- AD LF G LLI'A.

